1. Technical Field
This application relates to a compact cylindrical form factor antenna suitable for use in satellite communications and other applications.
2. Background Information
In certain applications of radio communications it is important to be able to robustly communicate without knowing the relative orientation of the transmit and receive antennas in advance. For example, in the case of communication from a satellite to a terrestrial vehicle, as the vehicle moves about the terrain (or even within a building), signals arrive at the antenna on the vehicle with a variety of different polarizations from different directions. If the vehicle uses, for example, a simple vertical dipole, one obtains 360° coverage but only for vertically polarized signals. Such a vertical dipole is relatively insensitive to horizontally polarized signals.
Many antennas mounted on vehicles also take the form of a mast that may be purposely flexible so that if the antenna hits an object it will bend and not snap or break. Antennas formed with flexible masts thus have their vertical and/or horizontal orientation direction altered by the flexibility of the mast, meaning that reliable communication cannot always be established if the polarization direction of the antenna is not exactly aligned with that of the transmitter. In short, it is often the case that as a vehicle moves throughout an environment, its antenna may tilt at various angles and therefore compromise communications with either a terrestrial base station or a satellite.
It is known that an Orientation-Independent Antennas (ORIAN) can be formed from crossed vertical loops in combination with one or more horizontal loops. This arrangement may provide circular polarization in a hemisphere surrounding the antenna such that signals are robustly received regardless of their polarization or angle of arrival. The antenna can be a free standing antenna.
One such ORIAN antenna is in the form of a cube with the various loops implemented as triangular shaped antenna elements disposed on the surfaces of the cube. Such antennas are described in further detail in U.S. patent application Ser. No. 13/404,626 filed on Feb. 24, 2012 by Apostolos, et al. the entire contents of which are hereby incorporated by reference.